Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1752662AbdLFVko (ORCPT ); Wed, 6 Dec 2017 16:40:44 -0500 Received: from merlin.infradead.org ([205.233.59.134]:32872 "EHLO merlin.infradead.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752373AbdLFVkZ (ORCPT ); Wed, 6 Dec 2017 16:40:25 -0500 Date: Wed, 6 Dec 2017 22:40:08 +0100 From: Peter Zijlstra To: Cheng Jian Cc: tglx@linutronix.de, mingo@redhat.com, dvhart@infradead.org, linux-kernel@vger.kernel.org, xiexiuqi@huawei.com, huawei.libin@huawei.com Subject: Re: [PATCH] futex: use fault_in to avoid infinite loop Message-ID: <20171206214007.GI3857@worktop> References: <1512570067-79946-1-git-send-email-cj.chengjian@huawei.com> <20171206160400.yzewed5juhytfwyy@hirez.programming.kicks-ass.net> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20171206160400.yzewed5juhytfwyy@hirez.programming.kicks-ass.net> User-Agent: Mutt/1.5.22.1 (2013-10-16) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 2106 Lines: 65 On Wed, Dec 06, 2017 at 05:04:00PM +0100, Peter Zijlstra wrote: > On Wed, Dec 06, 2017 at 10:21:07PM +0800, Cheng Jian wrote: > > It will cause softlockup(infinite loop) in kernel > > space when we use SYS_set_robust_list in futex which > > incoming a misaligned address from user space. > > Urgh, we should not allow that in the first place. > > See how get_futex_key() does: > > if (unlikely(address % sizeof(u32))) > return -EINVAL; > > That same should also be true for the robust list. Using unaligned > variables is insane. Something a little like so perhaps.. --- Subject: futex: Sanitize user address in set_robust_list() Passing in unaligned variables messes up cmpxchg on a whole bunch of architectures. Also, not respecting the natural alignment of data structures is pretty dumb to begin with. Signed-off-by: Peter Zijlstra (Intel) --- include/uapi/asm-generic/errno.h | 1 + kernel/futex.c | 5 +++++ 2 files changed, 6 insertions(+) diff --git a/include/uapi/asm-generic/errno.h b/include/uapi/asm-generic/errno.h index cf9c51ac49f9..4cb80d4ac160 100644 --- a/include/uapi/asm-generic/errno.h +++ b/include/uapi/asm-generic/errno.h @@ -119,5 +119,6 @@ #define ERFKILL 132 /* Operation not possible due to RF-kill */ #define EHWPOISON 133 /* Memory page has hardware error */ +#define EMORON 134 /* User did something particularly silly */ #endif diff --git a/kernel/futex.c b/kernel/futex.c index 76ed5921117a..e2c1a818f88f 100644 --- a/kernel/futex.c +++ b/kernel/futex.c @@ -3262,6 +3262,8 @@ static int futex_wait_requeue_pi(u32 __user *uaddr, unsigned int flags, SYSCALL_DEFINE2(set_robust_list, struct robust_list_head __user *, head, size_t, len) { + unsigned long address = (unsigned long)head; + if (!futex_cmpxchg_enabled) return -ENOSYS; /* @@ -3270,6 +3272,9 @@ SYSCALL_DEFINE2(set_robust_list, struct robust_list_head __user *, head, if (unlikely(len != sizeof(*head))) return -EINVAL; + if (unlikely(address % __alignof__(*head))) + return -EMORON; + current->robust_list = head; return 0;